Encapsulated materials have been used for many years in a wide variety of commercial applications. Early uses of encapsulated materials included paper coated with capsules bearing coloring material therein which could be used as a recording medium. U.S. Pat. No. 3,016,308 discloses one of the early efforts using encapsulated material as the image source on recording paper. U.S. Pat. Nos. 4,058,434 and 4,201,404 disclose other methods of application of encapsulated coloring materials on paper substrates to be used as imaging media and the like. U.S. Pat. No. 3,503,783 discloses microcapsules with a metal coating on the surface of the capsule, having coloring material therein which are rupturable by the application of heat, pressure and/or radiation. These rupturable microcapsules, in one embodiment, may be secured between a substrate and a photoconductive top coat to enable photosensitive imaging of the system.
Encapsulation technology has also been used to produce tamper-evident constructions. For example, Charbonneau discloses in U.S. Pat. No. 4,988,557 fragrance-releasing pull-apart sheets, which provide fragrance release upon separation. The sheets comprise microcapsules between two surfaces, with a discontinuous binder, the surfaces being adhered together by the binder. Patentees indicate that the capsule-bearing adhesive layer in their construction may be used as a security device for an article such as a coupon, lottery ticket or gaming card, in which, once the article has been opened and fragrance released, subsequent failure to release fragrance would alert any recipient to prior use and to the possibility of tampering. Additionally, Cornell discloses in U.S. Pat. No. 3,896,965 a tamper indicator tape for hermetically sealed containers having the aperture covered by a tape closure. The tape closure has on its outer surface an indicator layer which changes color when flexed, indicating whether the closure has been handled or tampered with. The indicator layer comprises binder resin, reactant materials and optional filler. The reactant materials comprise components that will react with one another to form a dye. One of these reactive components is encapsulated. The binder resin is selected to have a high enough tensile or Young's modulus that the force exerted to flex the closure tab upon opening will rupture the enclosed capsules. See column 2, lines 25-28.